for me it's internal/external parts & ship rate
gun prices would never be great, if you can somehow make them lower, then well, great for customers...
all it comes down to is prices..because I swear sometimes even with the exchange rate right now, still cheaper to buy in the states. (cheaper same brand parts, super cheap shipping[free-$5] and I can pick it up and throw it into my tool box..) Only so far one Canadian store I know who does flat $10 or free orders over $200 for shipping, and I love that..
customer support is important too...i had many times where I asked for a part if they carry or order just to get no replies...only if i'm lucky, so off to states I go...again..